In recent times, the number of pixels handled by digital image processing is increasing from year to year in connection with the adoption of 4k2k (3840×2160 pixels) for displays for general users, HD (High Definition: 1920×1080 pixels) for broadcasting and high pixel capacities for image sensors and displays of digital video cameras.
Regarding formulas of transmitting such image data between equipment units, there are the HDMI (High-Definition Multimedia Interface (registered trademark of HDMI Licensing, LLC) standards and DisplayPort (registered trademark or trademark of VESA) standards formulated by VESA (Video Electronics Standards Association).
Regarding the aforementioned HDMI data transmission formula, Patent Literature 1 states that it is “to selectively transmit uncompressed image signals or compressed image signals obtained by subjecting these uncompressed image signals to compression processing by a compression formula compatible with the receiver device, and permits satisfactory transmission of image signals at a desired bit rate within the transmission bit rate range of the transmission path” (see [0048] in Patent Literature 1) and, regarding the compression formula, “the data compressors 121-1 to 121-n process compression, at a prescribed compression rate, of uncompressed image signals outputted from the codec 117 and outputs compressed image signals. The data compressors 121-1 to 121-n constitute an image signal compressing unit. Each of the data compressors 121-1 to 121-n processes data compression by a different compression formula from all the others. For instance, it is stated that, as compression formulas, “‘RLE (Run Length Encoding)’, ‘Wavelet’, ‘SBM (Super Bit Mapping (trademark of Sony))’, ‘LLVC (Low Latency Video Codec)’, ‘ZIP’ and so forth are conceivable” (see [0077] in Patent Literature 1).
Further in HDMI, data transmission formats of TMDS (registered trademark of Transition Minimized Differential Signaling (Silicon Image, Inc.)) are used for image data, and Patent Literature 2 is cited as one example.